Method of treating gluten

ABSTRACT

1. A METHOD FOR THE PREPARATION OF A PROTEINACEOUS COMPOSITION SUITABLE FOR USE AS A FOOD MATERIAL COMPRISING (1) PREPARING A MIXTURE CONSISTING ESSENTIALLY OF GLUTEN AND METHANOL AT A TEMPERATURE OF FROM ABOUT 20* C. TO ABOUT 40* C., SAID MIXTURE CONTAINING LESS THAN ABOUT 10% WATER, BASED ON METHANOL, (2) SEPARATING SAID GLUTEN FROM SAID METHANOL BY MEANS OF COUNTERCURRENT EXTRACTION, FILTRATION OR CENTRIFUGATION, (3) MIXING SAID GLUTEN WITH AQUEOUS METHANOL CONTAINING FROM ABOUT 10% TO ABOUT 25% WATER, (4) HEATING THE RESULTING MIXTURE AT FROM ABOUT 110* C. TO ABOUT 140* C. FOR FROM ABOUT 1 TO ABOUT 5 MINUTES, (5) SEPARATING AN AQEOUS METHANOL EXTRACT FROM THE SOLID RESIDUE AT A TEMPERATURE OF FROM ABOUT 60* C. TO ABOUT 140* C., AND (6) ISOLATING A PROLAMINE FROM SAID AQUEOUAS METHANOL EXTRACT.

United States Patent 3,840,515 METHOD OF TREATING GLUTEN Robert A.Reiners, Hinsdale, John C. Pressick, Clarendon Hills, and Leo Morris,Lincolnwood, Ill., assignors t0 CPC International Inc. No Drawing. FiledFeb. 7, 1972, Ser. No. 224,254 Int. Cl. A23j 1 12; C07g 7/00 US. Cl.260112 G 3 Claims ABSTRACT OF THE DISCLOSURE The invention of thisapplication relates to the preparation of relatively oil-free glutenmaterials. It relates more particularly to such oil-free glutenmaterials which are also substantially reduced with respect to the colorand flavor normally associated with gluten. Still more particularly, itrelates to a novel method for the preparation of prolamines from gluten.

Of the three principal classes of foods, i.e., proteins, carbohydratesand fat, proteins constitute the most important class because theyprovide the amino acids from which body tissues are made. All threeclasses, of course, are essential, but nature has made starches and fatsmore easily available than proteins. Shortages of starches and fats arevirtually unknown, but there are millions of people in the world who donot ingest suflicient quantities of protein in their diet to maintainnormal healthy growth.

The two principal sources of proteins are meats and grains. The formerare understandably less plentiful than the latter, but they are alsomore desirable. The conversion of grain protein to animal protein isexpensive, but the enhancement of flavor which accompanies suchtransformation is sufiicient to justify this expense.

One purpose of the invention herein is to upgrade the aestheticqualities of grain protein so as to render it suitable for incorporationinto animal protein in foods, viz, meat. Another purpose of theinvention is to make available a new, improved process for thepreparation of prolamines from gluten.

The oil content, the color and the flavor of gluten have long beenrecognized as undesirable components of this proteinaceous material andtheir removal has generally been accomplished by means of hexane.Originally, zein had been prepared by the aqueous ethyl alcohol extrac'tion of powdered corn. Osborne, in U.S. Pat. 456,773, first suggestedthe use of corn gluten as a source of zein. He taught the extraction ofzein from corn gluten by means of 95% ethyl alcohol. The resultingaqueous ethyl alcohol extract was separated by filtration, thenevaporated to dryness to yield the desired zein.

Swallen, US. Pat. 2,120,946, discloses a process for the preparation ofrelatively concentrated solutions of zein having reduced oil and colorcontent. The process consists in extracting corn gluten with an aqueousmixture of solvents. The mixture includes a lower aliphatic alcohol suchas ethyl or methyl alcohol plus an alcohol-miscible solvent for corn oiland coloring matter. This latter alcohol-miscible solvent may betoluene, benzene, xylene, chlorinated hydrocarbons or the like. Atypical such aqueous solvent mixture would contain 7-8% of water. Theresulting aqueous alcohol extract then is itself ex- Patented Oct. 8,1974 tracted with an additional amount of the above alcoholmisciblesolvent for corn oil and coloring matter, i.e., toluene, xylene,benzene, etc. The purpose of this second extraction is to remove the oiland coloring matter from the original aqueous alcohol extract. Theprincipal advantage of this method is the considerable savings inalcohol which must be used.

In another patent which issued about the same time, US. Pat. 2,133,591,Swallen discloses a quite similar process differing in that the solventemployed in the first extraction step is either a single solvent such asmethyl alcohol or a mixture of such alcohols. That is, the firstextracting solvent does not contain an oil-extracting solvent such astoluene, benzene or xylene.

Walsh et al., US. Pat. 2,360,381, disclose the preparation of zein fromcorn gluten by means of extraction of the gluten with a 40%65% aqueousmonohydric alcohol solvent. The alcohol may be methyl, ethyl, thepropyl, the butyl, and other appropriate alcohols used singly or inmixtures. The aqueous alcohol extract is cooled so as to effect phaseseparation between a heavier, relatively zein-rich layer and a lighter,relatively zein-poor layer. The heavier layer is then isolated and freedof solvent by evaporation.

While certain of the above disclosed processes, and many others as well,purportedly result in relatively oiland color-free products, the oil andcolor contents of such products still leave something to be desired.Furthermore, the above patents do not refer to the presence in gluten ofan undesirable feedy flavor. Such flavor has in the past relegated theseproteins to chemical uses or animal foods. It is a distinct barrier totheir use for human consumption.

It is accordingly a principal object of the present invention to providea relatively oil-free proteinaceous composition.

Another object is to provide such a composition which is also relativelycolorless.

Another object is to provide such a composition which is much reduced infeedy flavor with respect to the gluten from which it is prepared.

Another object is to provide an eflicient process for the preparation ofprolamines from gluten.

These and other objects are accomplished by the present inventionwherein gluten is extracted with substantially anhydrous methanol. Amixture of gluten and methanol is prepared, the mixture containing lessthan about 10% water based on methanol, and then separated to yield arelatively oil-free proteinaceous material. This material is suitablefor use in human food compositions, particularly in sausage and weinerformulations where it is effective as a binder material. It is alsouseful in hamburger formulations and in bread formulations.

The relative proportions of methanol and gluten will vary depending uponthe particular type of separation means employed. As little as threeparts of methanol per part of gluten may be employed and, on the otherhand, as much as 20 or 30 parts may thus be employed. All parts andpercentages herein, unless otherwise expressly stated, are by weight.

The means of separation of methanol from gluten is not critical and maybe either countercurrent extraction or batch extraction. A particularlydesirable means is that aflorded by a cyclone separator, becauserelatively small amounts of methanol are thus required. Where a batchmethod of separation is employed, i.e., filtration or centrifugation, itis necessary to use larger amounts of methanol ranging up to as much as20 to 30 parts per part of gluten. In such instances, it is ordinarilydesirable to use about 10 parts of methanol and then to wash the filtercake or solid centrifugate with an additional 10 3 a parts of me anoSm6times two washes are desirable. embodiment, the water content of theextracting mixture In still other instances, it is advisable tore-slurry the is less than about based on methanol. Particularly filtercake with fresh methanol and then to filter it again. preferred is theuse of 100% methanol and a gluten con- The time of contact betweengluten and methanol is taining about of wa A preferred embodimentcontemplates the use of an aqueous slurry of gluten as a raw material.Such aqueous not critical and will depend upon the particle size of thegluten. That is, the more finely divided the gluten,

the less time required for Contact With methanol to effect slurry isdewatered by extraction with methanol to an efficient extraction.Ordinarily, the two are contacted for overall Water content which bringsit within the Scope b t 10 minutes and It is unnewssal'y to extend P 3of the above limitations. The dewatering step must be of this step y i ll 2P ggzfgi 2 10 carried out rapidly so as to minimize losses toprolamine ture contains a t 21m6 Y arge P I by solution in the aqueousmethanol.

8l0%, then the time of contact should be short so as to minimize lossesof prolamine via solution in the watery The gluten may be derlved from yown source inmethanol. eluding P ipally, corn and wheat. Because the Theeffectiveness of methanol is surprising in view of problems of flavor211:6 e I SeIy associated w th com the relative ineffectiveness of otherlow molecular weight gluten, Process 15 p c ly effective where oalcohols. A comparison of the results of extraction of Pf IS the g t usd as the raw mater1a1, Th corn gluten by several low molecular weightalcohols is Posltlon of a ypl l corn gluten 1s 60% protein, 6% oil,shown in Table I. 24% starch and other carbohydrates and 10% water.

TABLE I.EFFICIENCY OF VARIOUS SOLVENTS IN DEOILING GLUTEN Oil in Proteinresidue lost Extract Flavor eal (percent color Color of of m Extractionconditions (P of ota (432 residue residue 1 None-Flash-dn'ed glutenMethanol-Cake washed with equal volnme I Ethanol-Cake Washed with equalvolume" 0"": D. o Do.

4 Hexane-Cake washed With equal volume 5 HexaneReslu.rried 3 times andcake washed each time..-

In each of Nos. 2, 3 and 4 above, gluten was ex- The preparation of anoil-free, colorless, bland gluten tracted via a batch process with 9parts of methanol, is shown below: ethanol and hexane, respectively,filtered, and the filter EXAMPLE 1 cake washed with 9 parts of freshmethanol. In No. 5, A Slurry of 100 Parts of a spraydried corn glutengluten was extracted with 9 parts of hexane, filtered, and 974% of whichpasses through a 20O mesh sieve, and the filter cake reslurried with anadditional 9 parts of 900 parts of methanol is Passed through a 5 stagey fresh hexane. This reslurrying step was repeated two more doneSeparator at C. The slurry product obtained u s, a total of 36 I?" ofhexarie was used d at the 5th stage is centrifuged, then dried overnightin It will be noted that the flash-dried gluten contame a vacuum oven atThe product is Substantially 9 of 011 Whereas F methanol'extlactedgluten00H- 40 colorless and oil-free and has a bland flavor. tamed but 05% of2 90% of the 011 havmg been. The above oil-free gluten is useful as anemulsifying moved by such extraction. Furthermore, the extractions agentin Sausage formulations, as illustrated by the with ethanol and hexanewere much less effective than lowing composition: the methanolextraction, producing gluten products hav- SAUSAGE ing 1.1%, 2.1% and2.0% of oil. Still further, it will be Percent seen that only themethanol extraction yielded a product Fat 30 having a white color and abland flavor. The others all gave a yellow color and a feedy flavor.Meat pgtein T 10 It is apparent that methanol has a unique solubilizingSalt 2 character with respect to the above undesirable con- Dextrose 3stituents of gluten. f h 1 th 50 Flavorings 2 The tern erature o t eextraction is convenient y wi in the rangg of from about 15 C. to about40 C. Tem- 011 free gluten pfoduct of Examp 1e 1 3 peratures above 40 C.permit the extraction of an undue As noted earlier, another aspect ofthe invention is the amount of zein from the gluten and thus diminishthe P p n of prolamines from gluten. The method of yield of desiredoil-free proteins. Temperatures below Preparation involves mixiflg theabove Oil-free gluten With 20 C. do not help in this respect and it isthus unnecessary zgl me g ol corllltalningl from about 10? to agent toresgrt to li 0 water, eating t e resu ting mixture at rom a out Thewater contest of the extraction method is an im- 0 C. to about 140 C.for from about 1 to ab 5 portant factor. Although zein and gliadin areprolamines mlflufe, separatlng an aqueous an l extract from d are h l bli aqueous l h l they are t the solid residue at a temperature of fromabout 60 C. sufficiently readily soluble in 90% aqueous methanol as toabout and Isolating a prolamillfi3 from Said to defeat the purposes ofthis invention. On the other methanol eXtracthand, an extraction mixturecontaining more than 10% A tyPlcal Preparatlon of a prolamine y theabove water is unsatisfactory because increasing amounts of Process 15as follows! zein are soluble in aqueous methanol as the proportion ofwater is increased beyond about 10%. Ordinarily, the EXAMPLE 2 glutenwhich is used as the raw material in the process A slurry of 300 partsof the oil-free product of Examcontains about 10% moisture, but becausethe amount of ple 1 in 1500 parts of aqueous methanol is stirredmethanol used is significantly greater than the amount at 130 C. in apressure vessel for two minutes, then of gluten used, this proportion ofmoisture in the gluten "0 cooled quickly to 60 C. and filtered. Thefiltrate is treatdoes not ordinarily become a factor in this regard. Ated with five parts of ION sodium hydroxide and heated the same time, ifaqueous methanol is to be used as with stirring at C. for two minutes.This solution the solvent, then the moisture content of the gluten mustthen is cooled, filtered, cooled further to -25 C. and be considered soas to keep the overall water content of neutralized by the addition,with continued stirring, of

the extracting mixtur below about 10%, In a preferred 75 four parts ofconcentrated hydrochloric acid. The resulting slurry is cooled stillfurther to 35 C. and filtered. The prolamine (zein) precipitate iswashed with 85% aqueous methanol, then with 100% methanol, all at -35 C.Then the washed solid is warmed to room temperature and washed againwith 100% methanol, then dried. The product is the desired zein.

The oil-free gluten may, as before, be any of the variously availableglutens, e.g., from wheat or corn. In the case of wheat, the desiredprolamine is gliadin; in the case of corn, it is zein. Where it is corngluten, and the desired product is zein, isolation of the zein from theaqueous methanol extract may be carried out by known procedures, asindicated in the above patents, or certain novel techniques may beemployed as described hereinafter.

Aqueous methanol solutions of zein tend to gel. Ordinarily, thistendency can be avoided by treating the aqueous methanol solution withalkali. We have found that by increasing the temperature at which suchtreatment ordinarily is effected we can decrease considerably the timerequired for such treatment. Where previously, it was thought necessaryto treat an aqueous alcoholic solution of zein with about 2% of sodiumhydroxide based on the amount of zein for 30 minutes at refluxtemperature to accomplish the desired modification, the same result canbe achieved by heating the same mixture at 100 C. for as short a time astwo minutes. This represents a remarkable saving in time, andsignificantly less alkali can be used to achieve a satisfactory degreeof modification, i.e., the aqueous methanol solution is renderedsuitably immune to gelatinization. The degree of modification isreflected by the salt point value of the solution, a high salt pointvalue representing a high degree of modification and a correspondinglyhigh degree of immunity to gelatinization. Salt point is the ionicstrength at which clouding occurs when a 1% solution of prolamine in0.05N sodium hydroxide is titrated with a solution of 1.0N in sodiumchloride and 0.05N in sodium hydroxide, at 25 C. It is determinedaccording to the following formula:

Titer in ml. Titer plus 25 In addition to sodium hydroxide, eitherpotassium hy droxide or calcium hydroxide may be used to accomplish theabove desired modification.

Then, the modified aqueous methanol solution of zein may be neutralizedwith dilute hydrochloric acid and quenched in a large volume of water atC. or, alternatively, the modified aqueous methanol solution is cooledto about C., then neutralized with dilute hydrochloric acid to a pH ofabout 6, cooled further to about -35 C. and filtered. The temperature atwhich neutralization is effected in the latter alternative process issomewhat critical, too low a temperature resulting in an ultimately slowfiltration rate and too high a temperature resulting in the formation ofa gummy precipitate. The filtration at about 35 C. proceeds rapidly andyields Salt Point= plus 0.05

a particulate precipitate. This may be washed at -35 C. with additionalaqueous methanol so as to remove the salt formed on neutralization ofthe alkali. The zein then may be dewatered and dried by ordinary meanssuch as flash drying so as to remove residual methanol and water.

In still another embodiment of the invention, the above precipitate,obtained at 35 C., is allowed to warm to about 30 C., at which point itis a viscous fluid. Then it is poured into a large volume of vigorouslyagitated cold (10 C. or lower) water whereupon it solidifies.

While the invention has been described in connection with specificembodiments thereof, it will be understood that it is capable of furthermodification, and this applilation is intended to cover any variations,uses, or adaptations of the invention following, in general, theprinciples of the invention and including such departures from thepresent disclosure as come Within known or customary practice in the artto which the invention pertains and as may be applied to the essentialfeatures hereinbefore set forth, and as fall within the scope of theinvention.

What is claimed is:

1. A method for the preparation of a proteinaceous composition suitablefor use as a food material comprising (1) preparing a mixture consistingessentially of gluten and methanol at a temperature of from about 20 C.to about 40 C., said mixture containing less than about 10% water, basedon methanol, (2) separating said gluten from said methanol by means ofcountercurrent extraction, filtration or centrifugation, (3) mixing saidgluten with aqueous methanol containing from about 10% to about 25%water, (4) heating the resulting mixture at from about C. to about C.for from about 1 to about 5 minutes, (5) separating an aqueous methanolextract from the solid residue at a temperature of from about 60 C. toabout 140 C., and (6) isolating a prolamine from said aqueous methanolextract.

2. The method of claim 1 wherein the separation of gluten from methanolin step (2) is accomplished by means of countercurrent extraction.

3. The method of claim 1 wherein the gluten is corn gluten.

References Cited UNITED STATES PATENTS 2,120,946 6/1938 Swallen 260-1232,133,591 10/1938 SWallen 260-123 2,354,393 7/1944 Manley et a1. 260-1232,360,381 10/1944 Walsh et a1. 260-123 2,801,235 7/1957 Miley 260-112 G2,801,236 7/1957 Miley 260-112 G 3,100,710 8/1963 Carlin 99-107 JAMES R.HOFFMAN, Primary Examiner US. Cl. X.R. 260-123; 426-430

1. A METHOD FOR THE PREPARATION OF A PROTEINACEOUS COMPOSITION SUITABLEFOR USE AS A FOOD MATERIAL COMPRISING (1) PREPARING A MIXTURE CONSISTINGESSENTIALLY OF GLUTEN AND METHANOL AT A TEMPERATURE OF FROM ABOUT 20* C.TO ABOUT 40* C., SAID MIXTURE CONTAINING LESS THAN ABOUT 10% WATER,BASED ON METHANOL, (2) SEPARATING SAID GLUTEN FROM SAID METHANOL BYMEANS OF COUNTERCURRENT EXTRACTION, FILTRATION OR CENTRIFUGATION, (3)MIXING SAID GLUTEN WITH AQUEOUS METHANOL CONTAINING FROM ABOUT 10% TOABOUT 25% WATER, (4) HEATING THE RESULTING MIXTURE AT FROM ABOUT 110* C.TO ABOUT 140* C. FOR FROM ABOUT 1 TO ABOUT 5 MINUTES, (5) SEPARATING ANAQEOUS METHANOL EXTRACT FROM THE SOLID RESIDUE AT A TEMPERATURE OF FROMABOUT 60* C. TO ABOUT 140* C., AND (6) ISOLATING A PROLAMINE FROM SAIDAQUEOUAS METHANOL EXTRACT.